In the EFI shell, if you enter FS0:\System\Library\Coreservices\boot.efi (it may be FS1:, FS2: &c depending on the order of your virtual disks) it will run. Unlike a real mac the firmware doesn't know where to look. The ISO produced will work fine with VirtualBox but will not run automatically as Apple have put boot.efi in a non-standard place. Virtualization core: Fixed macOS Catalina guests failing to boot after upgrading to 10.15.2 onwards (bug # 19188)įor versions of VirtualBox prior to 6.1.4 the following steps are required: You must tell VirtualBox what to boot These steps work absolutely fine to create an ISO but you have 2 issues which are resolved in VirtualBox 6.1.4 - from the changelog Mv ~/Desktop/Catalina.cdr ~/Desktop/Catalina.iso Hdiutil convert /tmp/Catalina.dmg -format UDTO -o ~/Desktop/Catalina.cdr Hdiutil detach /volumes/Install\ macOS\ Catalina Sudo /Applications/Install\ macOS\ Catalina.app/Contents/Resources/createinstallmedia -volume /Volumes/Catalina -nointeraction Hdiutil attach /tmp/Catalina.dmg -noverify -mountpoint /Volumes/Catalina hdiutil create -o /tmp/Catalina -size 9500m -volname Catalina -layout SPUD -fs HFS+J Note: I have increased the size of the /tmp/Catalina.dmg from 9000m to 9500m so it is big enough to fit 10.15.5. dmg is too small the subsequent createinstallmedia command will fail with "Error erasing disk error number (22, 0)" Note: I have increased the size of the /tmp/Catalina.dmg from 8500m to 9000m so it is big enough to fit 10.15.4 (previous versions worked fine).
The command you mention in your comments hdiutil create -o /tmp/Catalina -size 8500m -volname Catalina -layout SPUD -fs HFS+J appears to come from this tutorial which in full does this: